The fast uptake of 3GPP Long Term Evolution (LTE) in different regions of the world shows both that demand for wireless broadband data is increasing, and that LTE is an extremely successful platform to meet that demand. Existing and new spectrum licensed for exclusive use by IMT technologies will remain fundamental for providing seamless coverage, achieving the highest spectral efficiency, and ensuring the highest reliability of cellular networks through careful planning and deployment of high-quality network equipment and devices.
To meet ever increasing data traffic demand from users and, in particular, in concentrated high traffic buildings or hot spots, more mobile broadband bandwidth will be needed. Given the large amount of spectrum available in the unlicensed bands around the globe as shown in FIG. 1, unlicensed spectrum is more and more considered by cellular operators as a complementary tool to augment their service offering. FIG. 1 discloses the unlicensed spectrum in 5 GHz available in selected countries or regions, such as Korea, China, Japan, the US and the European Union. While an unlicensed spectrum can never match the qualities of the licensed regime, solutions that allow an efficient use of it as a complement to licensed deployments have the potential to bring great value to the 3GPP operators, and, ultimately, to the 3GPP industry as a whole. This type of solutions would enable operators and vendors to leverage the existing or planned investments in LTE and 3GPP Evolved Packet Core (EPC) hardware in the radio and core network.
The unlicensed spectrum in general allows non-exclusive use. Given the widespread deployment and usage of other technologies in unlicensed spectrum for wireless communications in our society, it is envisioned that LTE would have to coexist with existing and future uses of unlicensed spectrum. Some regulatory regime adopts technology-neutral coexistence policy. For instance, the US FCC Part 15.407 rule states “The primary operating condition for unlicensed devices is that the operator must accept whatever interference is received and must correct whatever interference it causes. Should harmful interference occur, the operator is required to immediately correct the interference problem or cease operation.”
However many jurisdictions require a Clear Channel Assessment (CCA) protocol, often referred to as Listen Before Talk (LBT). The basic LBT operation of LBT is to sense for energy on the shared channel and not transmit until there is no energy detected on the channel above an Energy Detection (ED) threshold.
The IEEE 802.11 Wi-Fi standard implements LBT. In addition to Energy Detection using Carrier-Sense Multiple Access (CSMA), Wi-Fi certified devices conforming to the IEEE 802.11 standard, implement a CCA protocol to specifically detect transmissions from other Wi-Fi certified devices known as preamble detection termed (CCA-PD) or Carrier Sense termed (CCA-CS). The CCA-PD protocol changes the behavior of the transmitters LBT protocol to avoid transmitting while another Wi-Fi certified device is transmitting. CCA-PD may be considered as a second level energy detection threshold, set to the sensitivity level of Wi-Fi certified devices. In IEEE 802.11, the ED threshold is specified at −62 dBm, while the CCA-PD threshold is specified to be at least −82 dBm. This means that transmissions from other Wi-Fi certified devices are given a 20 dB advantage over transmissions from non-Wi-Fi certified devices.
As a result, many vendors of devices which are not certified by the Wi-Fi Alliance, which may herein also be referred to as non-Wi-Fi certified devices, propose to use 802.11 transmitters to send 802.11 CTS packets in advance of their non-Wi-Fi certified transmissions in the unlicensed spectrum, thus protecting the non-Wi-Fi certified transmission down to the lower CCA-PD threshold. For example, some vendors of LTE-U and LTE-LAA eNBs have added this capability to their products.
Various standards bodies such as 3GPP and MuLTEfire allow this capability as an optional feature. The Institute of Electrical and Electronics Engineers (IEEE), the Wi-Fi Alliance (WFA), and equipment vendors in the Wi-Fi industry are calling for this capability to be made mandatory in regulations and standards specifications. They want to ensure that e.g. LTE Licensed Assisted Access (LAA) and other non-Wi-Fi technologies do not have an advantage over Wi-Fi. Thus they prefer that all devices operate like Wi-Fi certified devices, i.e. transmit Wi-Fi 802.11 preambles and use the 802.11 ED and PD thresholds.
Some non-Wi-Fi certified equipment may transmit 802.11 signals in order to gain the 20 dB protected advantage that 802.11 provides to other Wi-Fi certified devices but there is no requirement for non-Wi-Fi certified equipment to act reciprocally, i.e. to decode 802.11 signals. The non-Wi-Fi certified equipment, which may herein also be referred to a device, may be of any technology not being conform with the IEEE 802.11 standard, including but not limited to LTE in Unlicensed spectrum (LTE-U) eNBs, LTE Licensed Assisted Access (LAA) eNBs, LTE LAA User Equipment (UE) or MuLTEfire Access Points (APs) or MuLTEfire UEs. The device m
This has the effect that the non-Wi-Fi certified equipment is gaining another 10 dB advantage, thereby putting Wi-Fi certified devices at a 10 dB disadvantage over non-Wi-Fi certified devices that transmit but do not decode 802.11 signals compared to genuine Wi-Fi certified nodes. Since the 802.11 transmissions by the non-Wi-Fi certified nodes appear as genuine Wi-Fi certified transmissions, there has been no way of detecting such a situation.